I heard a homily on Sunday that made the point that, in our finite world, to choose something is to reject something else, and that it's the sorrow of having to reject those other things that can make choosing one thing hard. This is true whether there is only one morally permissible choice or several.
(Hence, perhaps, the popularity of cheap buffet restaurants. The appeal lies in the freedom from choice; it certainly can't be the quality of the food.)
I wondered whether that might be the point of creating a new heavens and a new earth at the end of the age. Might it be that, in the new creation, to choose something is somehow not to reject something else? If happiness is having what you want and wanting what you have, then maybe the wedding feast of Christ and His Church is a buffet, with the sort of food you'd expect God to serve at His Son's wedding feast.
Then, coincidentally, I came across this old post of mine, on the suggestion by Fr. John Corbett, OP, that (in my paraphrase) "God's promises are so wonderful the earth as it presently exists cannot contain them." Which, for what it's worth, is certainly consistent with the notion of choice without possibility of sadness.